This paper presents results from an experimental investigation carried out to study the potential use of copper slag as fine aggregate on the strength of both normal and high strength concrete. Concrete mixtures were prepared using different proportions of copper slag as partial and full replacement of fine aggregate. The percentage of copper slag added by weight ranged between 10-100% of sand used in concrete. For each concrete mixture, six 150mm× 150mm×150mm cubes, three 300mm×150mm dia. cylinders and three 100mm×100mm×500mm prisms were cast. Density, compressive, tensile and flexural strengths were determined at 28-day of curing. Cube compressive strength was also determined at 7-day of curing. Results demonstrated that there is general an increase in the density and workability of both normal and high strength concretes as copper slag quantity increases. Also results showed that the compressive strength of concrete is generally improved, compared with the control mix, with the increase of copper slag up to a certain copper slag content beyond which the strength generally reduces. Mixes with large copper slag percentage showed signs of bleeding and segregation due to the significant increase of workability.